Performance Enhancement Using Different Nitromethane Blends in a Small Two-Stroke Engine

Abstract

Abstract Nitromethane being immiscible in gasoline is often added to methanol to enhance the engine power output. But with the use of methanol as the base fuel, the brake specific fuel consumption (BSFC) of the spark ignition (SI) engine often doubles due to its lower heating value. To constrain this increase to a marginal value, a tri-component fuel blend consisting of nitromethane-alcohol-gasoline was prepared and observed to be stable. Methanol, ethanol, and butanol were the chosen alcohols for the tests due to their popularity as alternate fuels for SI engines. Tests on a small (35cc) two-stroke SI engine revealed that the torque produced with the use of tri-component blends was comparable with nitromethane-methanol blend and was on an average 1.35 times higher than gasoline. However, the BSFC with the nitromethane-butanol-gasoline blend was 50% lower than nitromethane-methanol blend and was only 14% higher than gasoline. The emission analysis showed lower HC emissions with the tri-component blends proving the improved combustion efficiency due to better mixing of the fuel-air mixture. Combustion analysis showed the increased heat release rate with nitromethane addition due to its higher flame speeds.